Medical devices

ABSTRACT

Medical devices and related methods are disclosed. In some embodiments, a method of manufacturing a medical device or a medical device component includes contacting a non-fluid first member and a second member, the first member comprising a first polymer and an alignable material different from the first polymer; aligning the alignable material; and bonding the first and second members together.

RELATED APPLICATIONS

This application is a continuation-in-part of and claims priority toU.S. patent application Ser. No. 10/936,042, filed on Sep. 8, 2004,which published as U.S. Patent Application Publication No. US2006/0051535 A1 on Mar. 9, 2006, and which is incorporated herein byreference in its entirety.

TECHNICAL FIELD

The invention relates to medical devices (e.g., medical tubing, guidewires, catheters, balloon catheters, stent-grafts, stents), and torelated methods.

BACKGROUND

Intravascular medical devices such as, for example, guide wires,catheters, and medical tubing, allow physicians to perform a medicalprocedure, such as balloon angioplasty (e.g., percutaneous transluminalcoronary angioplasty) or delivery of an endoprosthesis (e.g., a stent).In some cases, a device is inserted into a patient's vascular system ata convenient site and subsequently delivered (e.g., pushed) through thevascular system to a target site. The path that the device takes throughthe vascular system to the target site can be relatively tortuous, forexample, requiring the device to change direction frequently.

In some circumstances, it is desirable for the device to have relativelygood flexibility so that it can track along the tortuous path. At thesame time, the device preferably has good pushability so that forcesapplied proximally to the device can be transmitted distally to deliverthe device.

SUMMARY

The invention relates to medical devices.

In one aspect, the invention features a method of manufacturing amedical device or a medical device component, the method includingextruding a first polymer that includes a magnetically alignablematerial, and applying a magnetic field to the magnetically alignablematerial as the first polymer is extruded in a liquid state. The methodalso includes solidifying the first polymer to form the medical deviceor the medical device component.

In another aspect, the invention features a method of making a medicaldevice or a medical device component, the method including orienting afirst magnetically alignable material in a first composition that is ina liquid state and that includes a first polymer and the firstmagnetically alignable material. The method also includes solidifyingthe first composition to form the medical device or the medical devicecomponent.

In an additional aspect, the invention features a medical device with afirst portion including a first magnetically alignable material that isoriented in one direction. The medical device also has a second portionincluding a second magnetically alignable material that is not orientedin the same direction as the first magnetically alignable material.

In a further aspect, the invention features a medical device with afirst portion including magnetically alignable fibers that have anon-random orientation within the first portion, and a second portionthat is adjacent to the first portion.

In another aspect, the invention features a medical device with atubular member including magnetically alignable fibers. The magneticpermeability of a first portion of the tubular member is different fromthe magnetic permeability of a second portion of the tubular member.

In an additional aspect, the invention features a medical device with afirst portion and a second portion. The first portion includesmagnetically alignable particles that are collectively oriented in afirst direction, and the second portion includes magnetically alignableparticles that are not collectively oriented in the first direction.

Embodiments can include one or more of the following features.

The method can further include varying the magnetic field strength ofthe magnetic field. In some embodiments, the magnetic field can have amagnetic field strength of up to about 30 Tesla. In certain embodiments,the magnetic field can have a magnetic field strength of from about 25gauss to about 600 gauss. Applying a magnetic field to the magneticallyalignable material can include exposing the magnetically alignablematerial to a solenoid. Applying a magnetic field to the first polymercan include extruding the first polymer over a magnetic mandrel.

The method can further include extruding (e.g., intermittentlyextruding, continuously extruding) the first composition to form amember.

The medical device or the medical device component can be a catheter, aguide wire, a balloon, or an endoprosthesis delivery system. Inembodiments in which the medical device or medical device component is aballoon, the balloon can include one or more cutting elements. Themedical device or the medical device component can have a first portionand a second portion with different flexibilities and/or differentmagnetic permeabilities. The first portion and/or the second portion canhave a magnetic permeability of from about one to about 20 or from aboutfive to about 30. The medical device or the medical device component canhave a first portion including the magnetically alignable material, anda second portion that is substantially free of the magneticallyalignable material. The distal end of the medical device or the medicaldevice component can be more flexible than the proximal end. The firstportion and/or second portion of the medical device or medical devicecomponent can be a layer or section of the medical device or medicaldevice component.

The magnetically alignable material can be in the form of particles(e.g., spherical particles). The particles can have an average length offrom about 50 nanometers to about 25 microns. The particles can have anaverage width or diameter of from about five nanometers to about 25microns (e.g., from about 50 nanometers to about 25 microns). The methodcan further include orienting the particles in a first portion of themedical device or the medical device component to have a firstorientation, and orienting the particles in a second portion of themedical device or the medical device component to have a secondorientation that is different from the first orientation. The method caninclude orienting the particles in the first portion of the medicaldevice or the medical device component to have an orientation that isparallel or lateral to the longitudinal axis of the medical device orthe medical device component. The method can include orienting theparticles in the second portion of the medical device or the medicaldevice component to have a random orientation.

The magnetically alignable material can include one or morenanomaterials.

The concentration of the magnetically alignable material in the firstpolymer can be from about two weight percent to about 50 weight percent.The magnetically alignable material can include a ferromagneticmaterial. The first polymer can include a magnetorheological fluidincluding the magnetically alignable material.

The magnetically alignable material can be in the form of fibers. Thefibers can have an average aspect ratio of from about one to about 25.The fibers can have an average length of from about 50 nanometers toabout 25 microns, and/or an average width of from about five nanometersto about 25 microns.

Orienting the first magnetically alignable material can include varyingthe orientation of the first magnetically alignable material. Orientingthe first magnetically alignable material can include orienting thefirst polymer.

The method can further include coextruding (e.g., simultaneously orsequentially) a second polymer (e.g., as a layer) to form the medicaldevice or the medical device component. The first polymer can bedifferent from the second polymer. The second polymer can besubstantially free of magnetically alignable material.

The method can further include varying the thickness of the firstcomposition and/or the second composition in the member. The method canfurther include coextruding (e.g., intermittently coextruding,continuously coextruding) a second composition in a liquid state withthe first composition to form the member. The second composition caninclude a second polymer and a second magnetically alignable material.The method can further include orienting the second magneticallyalignable material in the second composition (e.g., so that the secondmagnetically alignable material has an orientation that is differentfrom the orientation of the first magnetically alignable material). Thefirst magnetically alignable material and the second magneticallyalignable material can be the same. The second magnetically alignablematerial can be randomly oriented. The second magnetically alignablematerial can be partially aligned relative to the first direction.

The second portion can be substantially free of magnetically alignablematerial. The second portion can be attached to the first portion. Thesecond portion can be integrally formed with the first portion. Thefirst portion can include a first polymer and the second portion caninclude a second polymer that is different from the first polymer. Thefirst portion and the second portion can be coextruded. The firstportion can include the magnetically alignable fibers and the secondportion can be substantially free of the magnetically alignable fibers.

The magnetically alignable particles can form at least one line that isoriented in the first direction. The magnetically alignable particlescan be randomly oriented.

The tubular member can consist essentially of a single composition. Thetubular member can have just one layer or more than one layer. Thetubular member can have a first layer that includes the magneticallyalignable fibers, and a second layer that is substantially free of themagnetically alignable fibers.

Embodiments can have one or more of the following advantages.

In some embodiments, a medical device (e.g., a catheter) that includesmagnetically alignable material can exhibit variable stiffness. Forexample, the proximal end of the medical device can be relatively stiff,while the distal end of the medical device can be relatively flexible.The relatively stiff proximal end can enhance the pushability of themedical device, such that the medical device can be easily pushed intothe body of a patient (e.g., without kinking or buckling). Therelatively flexible end of the medical device can enhance thetrackability of the medical device, such that the medical device can beeasily directed within the body of the patient. In certain embodiments,the medical device that exhibits variable stiffness can be formed bycontinuously extruding a polymer that includes magnetically alignablematerial embedded within it. A medical device that is formed of acontinuously extruded polymer can exhibit enhanced mechanical integrityrelative to a medical device that is formed of two or more differentpolymeric portions (e.g., that are butt welded to each other).

In one aspect, the invention features a method of manufacturing amedical device or a medical device component, the method includingcontacting a non-fluid first member and a second member, the firstmember comprising a first polymer and an alignable material differentfrom the first polymer; aligning the alignable material; and bonding thefirst and second members together.

Embodiments can include one or more of the following features. Thealignable material is aligned after contacting the first member and thesecond member. The alignable material is aligned magnetically. Thealignable material includes carbon, such as a carbon nanotube or acarbon fiber. The first member includes from about 2 to about 50 percentby weight of the alignable material. The first and second members areheld in contact by a heat shrink material. The first and second membersare bonded by heating at least one of the members. The first and secondmembers are bonded using a laser. The second member includes a secondpolymer and, optionally, a second alignable material. The first andsecond members are components of a balloon catheter.

In another aspect, the invention features a method of manufacturing amedical device or a medical device component, the method includingintroducing a first composition comprising a first polymer and analignable material into a cavity; aligning the alignable material; andsolidifying the first composition in the cavity.

Embodiments can include one or more of the following features. Thealignable material is aligned magnetically. The alignable materialincludes carbon, such as a carbon nanotube or a carbon fiber. The firstcomposition includes from about 2 to about 50 percent by weight of thealignable material. The first composition is solidified to form acomponent of a balloon catheter.

In another aspect, the invention features an endoprosthesis, theendoprosthesis including a metallic tubular structure; and a firstcomposition on the tubular structure, the first composition includes apolymer and an alignable material comprising a carbon nanotube or acarbon fiber aligned along a selected direction.

Embodiments can include one or more of the following features. The firstcomposition further includes a drug. The first composition includes fromabout 2 to about 50 percent by weight of the alignable material.

Other aspects, features and advantages of the invention will be apparentfrom the description of the preferred embodiments and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional side view of an embodiment of a ballooncatheter.

FIG. 2 is a perspective view of an embodiment of a tube for a ballooncatheter system.

FIG. 3A is an illustration of an embodiment of an apparatus for making atube for a balloon catheter system.

FIG. 3B is a side view of a portion of the apparatus of FIG. 3A.

FIG. 3C is a perspective view of a portion of the apparatus of FIG. 3A,when exposed to a magnetic field.

FIG. 3D is a perspective view of a portion of the apparatus of FIG. 3A,when extruding a material under exposure to a magnetic field.

FIG. 3E is a perspective view of a portion of the apparatus of FIG. 3A,when extruding a material under exposure to a magnetic field.

FIG. 3F is a perspective view of an embodiment of a tube for a ballooncatheter system.

FIG. 3G is a perspective view of a portion of the apparatus of FIG. 3A,when extruding a material that is not under exposure to a magneticfield.

FIG. 3H is a perspective view of an embodiment of a tubular member.

FIG. 4 is a detailed view of an embodiment of a method of making aballoon catheter.

FIG. 5 is a cross-sectional side view of an embodiment of a ballooncatheter.

FIG. 6 is schematic of an embodiment of a method of making a medicaldevice component.

FIG. 7A is a perspective view of an embodiment of a tube for a ballooncatheter system.

FIG. 7B is a cross-sectional side view of the tube of FIG. 7A, takenalong line 4B-4B.

FIG. 8A is a perspective view of an embodiment of a tube for a ballooncatheter system.

FIG. 8B is an exploded view of the tube of FIG. 5A.

FIG. 9 is a cross-sectional side view of an embodiment of a tube for aballoon catheter system.

FIG. 10 is an illustration of an embodiment of an apparatus for making atube for a balloon catheter system.

FIG. 11A is a cross-sectional side view of an embodiment of a balloon.

FIG. 11B is a cross-sectional side view of an embodiment of a balloon.

FIG. 12 is a perspective view of an embodiment of a tube for a ballooncatheter system.

FIG. 13A is a side view of an embodiment of an apparatus for making atube for a balloon catheter system.

FIG. 13B is a front view of the apparatus of FIG. 13A.

FIG. 14 is a perspective view of an embodiment of an endoprosthesis.

DETAILED DESCRIPTION

Referring to FIG. 1, a balloon catheter system 10 includes a catheter 12and an inflatable balloon 14 carried by the catheter. Catheter 12includes an outer shaft 16 and an inner shaft 18 defining a lumen 19.Shafts 16 and 18 are concentric and define an annular lumen 20 betweenthem. During use, catheter system 10 can be delivered to a treatmentarea (e.g., a coronary artery) by passing lumen 19 over a guide wire 22emplaced in the body, and pushing the catheter system to the treatmentarea. Balloon 14 can then be inflated or deflated by delivering orwithdrawing a fluid (such as a liquid or a gas) through annular lumen20. Examples of balloon catheter systems are described in U.S. Pat. Nos.5,195,969 and 5,270,086.

Referring now to FIG. 2, inner shaft 18 is tubular and is formed of acontinuously extruded polymer composite layer 30 that includes a polymermatrix 32 and magnetically alignable fibers 34 embedded in the polymermatrix. Inner shaft 18 has a relatively stiff proximal end 36 and arelatively flexible distal end 38. The magnetically alignable fibers inproximal end 36 are oriented parallel to the longitudinal axis “L” ofinner shaft 18, contributing to the relative stiffness of proximal end36. The magnetically alignable fibers in proximal end 36 have anon-random orientation because they have all been oriented substantiallyin the same direction. The magnetically alignable fibers in distal end38 are randomly oriented, contributing to the relative flexibility ofdistal end 38. The stiffness of proximal end 36 provides inner shaft 18with good pushability, while the flexibility of distal end 38 providesinner shaft 18 with good trackability. As shown in FIG. 2, theintermediate region 31 of inner shaft 18 does not include anymagnetically alignable fibers 34. However, in some embodiments (and asshown below), intermediate region 31 can include magnetically alignablefibers 34.

Referring to FIG. 3A, inner shaft 18 can be made, for example, using atube-forming apparatus 90. Tube-forming apparatus 90 includes anextrusion head 92, a quench tank 94, a laser micrometer 96, a puller 98,and a cut-off knife 100. Extrusion head 92 includes a housing 102 thatencloses three sections of the extrusion head: a magneticfield-generating section 110, a polymer feed section 120, and anextrusion die 126. Magnetic field-generating section 110 includes asteel sleeve 112, an iron tip guide 114, and a coil 116 (e.g., asolenoid) disposed between iron tip guide 114 and steel sleeve 112.Polymer feed section 120 includes a polymer feed 122 that, via a polymerfeed shaft 123, is in fluid communication with a hollow tip 124 thatextends through all three sections of extrusion head 92.

To form inner shaft 18, a polymer composite that includes a polymermatrix material and magnetically alignable fibers 34 is added intopolymer feed 122. While it is in polymer feed 122, the polymer compositeis melted to form a liquid polymer composite stream (e.g., amagnetorheological fluid) that flows through polymer feed shaft 123, andinto tip 124, exiting extrusion head 92 through extrusion die 126. Thepolymer composite stream starts to solidify upon exiting extrusion head92 through extrusion die 126, at which point the polymer compositestream is exposed to the ambient environment. As the polymer compositestream solidifies, it forms a tubular member 130. As the polymercomposite is being extruded, pressurized air (shown in FIG. 3A as asolid black line) flows through the center of hollow tip 124. Thepressurized air causes the polymer composite stream to form a tubularshape as it is extruded. As an alternative to pressurized air, in someembodiments, the polymer composite stream can be extruded over a mandrel(not shown) that causes the polymer composite stream to form a tubularshape when it is extruded. The mandrel can be formed of, for example,cast iron, carbon steel, or stainless steel (e.g., 306 stainless steel,316 stainless steel, 440C stainless steel). After exiting extrusion die126, tubular member 130 passes through quench tank 94, for furthercooling and solidification. Thereafter, tubular member 130 passesthrough laser micrometer 96, where it is sized, and through puller 98,which pulls tubular member 130 from extrusion die 126, through quenchtank 94 and laser micrometer 96, and directs tubular member 130 towardcut-off knife 100.

Referring now to FIG. 3B, the orifice of extrusion die 126 has adiameter D_(O), hollow tip 124 has an outer diameter OD_(H), and tubularmember 130 has an inner diameter ID_(T) and an outer diameter OD_(T).Operation of the puller 98 affects the draw-down ratio[(D_(O))/(OD_(T))] and the draw-balance ratio[((D_(O))/(OD_(T)))/((OD_(H))/(ID_(T)))] of tubular member 130. Inembodiments, the draw-down ratio of tubular member 130 can be from abouttwo to about 2.5. Alternatively or additionally, the draw-balance ratioof tubular member 130 can be from about 1.05 to about 1.1. Finally,tubular member 130 passes through cut-off knife 100, which cuts tubularmember 130 into smaller pieces, such as inner shaft 18. Inner shaft 18can then be incorporated into catheter system 10 by conventionalmethods. For example, inner shaft 18 can be attached to balloon 14 usingan adhesive, laser welding, and/or RF welding.

Suitable operating conditions for tube-forming apparatus 90, such aszone heating temperatures, polymer concentrations, feed rate, and linespeed, are described, for example, in Chin et al., U.S. Published PatentApplication No. 2002/0165523 A1, which is incorporated herein byreference in its entirety.

During the extrusion process, a magnetic field is applied to the polymercomposite stream to align the magnetically alignable material within thepolymer composite stream. Referring to FIG. 3A, coil 116 is selectivelyactivated (by passing electrical current through the coil) to alignmagnetically alignable fibers 34 within the polymer composite stream. Asshown in FIG. 3C, when coil 116 is activated, it generates a magneticfield force in the direction of arrows F. Iron tip guide 114 propagatesthe magnetic field along the length of tip 124, from the location ofcoil 116 to extrusion die 126. Thus, the polymer composite stream isexposed to the magnetic field as the polymer composite stream flowsthrough tip 124 and extrusion die 126. Exposure of the liquid polymercomposite stream to the magnetic field can cause magnetically alignablefibers 34 to respond by aligning themselves with the field. As shown inFIG. 3D, when coil 116 is activated during the formation of tubularmember 130, the resultant magnetic field causes magnetically alignablefibers 34 to become aligned parallel to the longitudinal axis “L1” oftubular member 130.

In some embodiments, and referring now to FIG. 3E, the resultantmagnetic field can cause magnetically alignable fibers 34 to line up ina “train” formation. The train formation can occur as a result of amagnetic dipole being formed along the axis of each fiber 34. Thismagnetic dipole causes the fibers to join end-to-end (e.g., in closeproximity, contacting), thereby forming a long, fibrous train of fibers34. In certain embodiments, a train formation can be created usingspherical magnetically alignable particles. For example, FIG. 3F shows ashaft 900 with a proximal end 902, a distal end 904, and a longitudinalaxis “L2”. Shaft 900 is tubular and is formed of a continuously extrudedpolymer composite layer 906 that includes a polymer matrix 908 andspherical magnetically alignable particles 910 embedded in the polymermatrix. While the magnetically alignable particles at distal end 904 arerandomly dispersed throughout polymer matrix 908, the magneticallyalignable particles at proximal end 902 have aligned so that they formlong trains 912 of the particles. Trains 912, which are orientedparallel to longitudinal axis “L2” of shaft 900, cause proximal end 902of shaft 900 to be relatively stiff. By contrast, distal end 904, withits randomly oriented particles, is relatively flexible. The formationof trains of magnetic particles is described, for example, in Cutillas &Liu, “Dynamics of Single Chains of Suspended Ferrofluid Particles,”presented at the Fourth Microgravity Fluid Physics & Transport PhenomenaConference (Aug. 12-14, 1998, Cleveland, Ohio), pages 100-105, which isincorporated herein by reference.

FIG. 3G shows that the deactivation of coil 116 results in magneticallyalignable fibers 34 having a random orientation, since they are nolonger exposed to a magnetic field. In some embodiments, activation ordeactivation of coil 116 can affect the concentration of magneticallyalignable fibers 34. For example, the magnetic field created by coil 116can pull magnetically alignable fibers 34 through the liquid polymercomposite as it is being extruded. When coil 116 is deactivated, thispulling force stops, such that magnetically alignable fibers 34 remainwhere they are in the polymer composite. Thus, a section of the extrudedtube that was formed while coil 116 was activated may have a higherconcentration of magnetically alignable fibers 34 than a section of theextruded tube that was formed while coil 116 was deactivated. A medicaldevice component such as inner shaft 18 can be formed by activating coil116 during one part of the extrusion process (e.g., during the formationof relatively stiff proximal end 36), and deactivating coil 116 duringanother part of the extrusion process (e.g., during the formation ofrelatively flexible distal end 38).

In some embodiments, and referring now to FIG. 3H, tubular member 130can be formed to have a relatively stiff proximal end 36, a relativelyflexible distal end 38, and an intermediate region 37 with a flexibilitybetween that of proximal end 36 and distal end 38. As shown,intermediate region 37 includes magnetically alignable fibers 34 thatall have the same orientation relative to longitudinal axis “L3” oftubular member 130, but that are not aligned parallel to longitudinalaxis “L3”. Intermediate region 37 of tubular member 130 can be formed,for example, as coil 116 is deactivated. Prior to deactivation of coil116, the magnetically alignable fibers 34 in intermediate region 37begin to become aligned relative to longitudinal axis “L3”. However,coil 116 is deactivated before the magnetically alignable fibers in theintermediate region can be aligned parallel to longitudinal axis “L3”.Thus, the magnetically alignable fibers in the intermediate region are“partially aligned” relative to longitudinal axis “L3”. Becauseintermediate region 37 includes magnetically alignable fibers with anintermediate alignment relative to the fibers in proximal end 36 anddistal end 38, intermediate region 37 has an intermediate flexibility,as well.

The strength of the magnetic field (e.g., created by a coil such as coil116) that is applied to magnetically alignable material can be selectedbased on the extent of alignment desired for the magnetically alignablematerial. In some instances, the strength of the magnetic field that isselected to induce a certain extent of alignment of the magneticallyalignable material may depend on the type of polymer in which themagnetically alignable material is embedded, and/or on the size of themagnetically alignable material. For example, a magnetic field with arelatively high magnetic field strength may be used to alignmagnetically alignable material (e.g., fibers, particles) that isrelatively small in size, and/or that is embedded in a polymer with arelatively high polymer melt viscosity. Another factor that mayinfluence the strength of the magnetic field selected to align themagnetically alignable material is the magnetic permeability of themagnetically alignable material. As an example, in some embodiments, amagnetic field with a relatively high magnetic field strength can beused to align iron particles that have a diameter of about one micronand that are suspended in a molten 72 durometer Pebax matrix. As anotherexample, in certain embodiments, a magnetic field with a relatively lowmagnetic field strength can be used to align iron particles that have adiameter of about ten microns and that are suspended in a low densitypolyethylene matrix. In some embodiments, the magnetic field (e.g.,created by a coil such as coil 116) that is applied to magneticallyalignable material can have a magnetic field strength of from about 25gauss to about 600 gauss (e.g., from about 100 gauss to about 400gauss).

While the above-described processes have been described with respect toinner shaft 18, in some embodiments, other components of ballooncatheter system 10 can alternatively or additionally be formed asdescribed above with respect to inner shaft 18. For example, outer shaft16 can include magnetically alignable material having differentorientations along the length of outer shaft 16. For example, ballooncatheter 14 can include magnetically alignable material having differentorientations along the length of the balloon.

In certain embodiments, a tubular component can be made with alignedmagnetically alignable materials, and can later be connected (e.g., bywelding) to a tubular component that does or does not include alignedmagnetically alignable material, to form a tubular member.

For example, balloon 14 can be formed, for example, by a blow moldingprocess in which the tubular member is placed (e.g., centered) in apreheated balloon mold, and air is introduced into the tube to maintainthe patency of the tube lumen. In some embodiments, after being soakedat a predetermined temperature and time, the tube can be stretched for apredetermined distance at a predetermined time, rate, and temperature.The pressure inside the tube can then be sufficiently increased toradially expand the tube inside the mold to form the balloon. The formedballoon can be heat treated, for example, to enhance folding memory,and/or folded into a predetermined profile. Methods of forming a balloonfrom a tube are described in, for example, Bertolino, U.S. Pat. No.6,946,092; Anderson, U.S. Pat. No. 6,120,364; Wang, U.S. Pat. No.5,714,110; and Noddin, U.S. Pat. No. 4,963,313.

After a balloon is formed, the balloon is secured to outer shaft 16.Referring to FIG. 4, balloon 14 including alignable material 26 isplaced coaxially around outer shaft 16 and temporarily secured in placeby placing a tube including a heat-shrink material 40 around the balloonand outer shaft and heating the tube. Examples of heat-shrink material40 include polyesters, nylons, polyamides, polyethylene terephthalate(PET), polybutylene terephthalate (PBT), PET-based elastomers, PBT-basedelastomers, thermoplastic polyurethanes, polyether block amide,polyolefins, polyvinyl chloride, fluoropolymers and mixtures thereof.Examples of fluoropolymers include fluorinated ethylene propylenecopolymer (FEP), polyvinylidene difluoride (PVDF) andpolytetrafluoroethylene (PTFE). Heat-shrink material 40 may include(e.g., be compounded with) non-stick additives, such aspolytetrafluoroethylene (PTFE) powder (Dupont) and/or silicones (DowCorning), to reduce the possibility of the tube becoming permanentlyintegral with balloon 14 during the bonding process, e.g., laserwelding.

Next, balloon 14 is bonded to outer shaft 16. As shown in FIG. 4, laserenergy (hv) can be used to bond or to weld balloon 14 to outer shaft 16.The laser energy is applied to balloon 14 and outer shaft 16 withsufficient energy to pass through tube including heat-shrink material40, thereby thermally bonding the balloon to the outer shaft at theinterface between the balloon and the outer shaft. Concurrently withapplying the laser energy, a magnetic field (B) is applied to balloon 14and outer shaft 16. As indicated above, during the bonding process, thepolymeric material of balloon 14 and/or outer shaft 16 can become moltenor partially molten, and consequently, the alignable material in thepolymer material can move out of a desired alignment. By applying themagnetic field, the alignable material in the molten or partially moltenpolymer material can be maintained in the desired alignment (as shown,parallel to the longitudinal axis of the balloon). By keeping alignablematerial aligned and strengthening balloon 14, adverse effect(s) fromlaser bonding (such as formation of heat-affected zone that may weakenthe balloon and/or its bond to outer shaft 16) can be reduced.Strengthening balloon 14 can be particularly desirable when the balloonis bonded to a portion of outer shaft 16 that has been thinned or neckedto bond with the balloon. In other embodiments, the magnetic field canbe applied to change the alignment of the alignable material from afirst alignment (e.g., prior to bonding) to a second alignment differentfrom the first alignment. The strength of the magnetic field applied canvary, as described above in the making of balloon 14. In otherembodiments, the magnetic field and the laser energy are applied in thealternating manner. As another example, other methods of bondingcomponents, such as RF welding, can be used.

Subsequent to bonding balloon 14 to the outer shaft 16, tube includingheat-shrink material 40 can be removed from bonded balloon 14 and outershaft 16 or kept in place, integral with the balloon catheter. Forexample, tube including heat-shrink material 40 can be removed bycreating score lines that extend radially toward the center of the tubeand longitudinally along the entire length or portions of the length ofthe tube. Scoring can make it easier and more controllable to removetube including heat-shrink material 40 in embodiments in which removalis desirable.

While the above-described processes have been described with respect toouter shaft 16, in some embodiments, other components of ballooncatheter 10 can alternatively or additionally be formed as describedabove with respect to outer shaft 16. As an example, referring to FIG.1, distal waist portion of balloon 14 can be bonded to inner shaft 18using the processes described above. As another example, FIG. 5 shows arapid exchange or single-operator exchange balloon catheter 51 includingan inner shaft 53, an outer shaft 55, and a balloon 57 bonded to theinner and outer shafts. Either or both shafts 53, 55 can include amixture of a polymeric material and an alignable material. A soft distaltip 59 configured to fit coaxially over inner shaft 53 is also bonded toinner shaft 53 to provide a non-traumatic distal end. The proximal endof inner shaft 53 is bonded to outer shaft 55 near opening 61 at alocation sometimes called a “port bond”, which can be formed using theprocesses described herein. Similarly, distal tip 59 can include amixture of a polymeric material and an alignable material and be bondedto inner shaft 53 using the processes described herein.

Other methods of making tubular members including a mixture of apolymeric material and an alignable material, such as the shaftsdescribed herein and distal tip 59, can also be used. For example, FIG.6 shows an injection molding apparatus 63 including components 65 thatengage together to form a cavity 67 and a port 69. Cavity 67 is sizedaccording to a desired component, such as distal tip 59 or balloon 14.Port 69 is used to introduce a composite mixture of a polymeric materialand an alignable material into cavity 67. To make a component, a liquidcomposite mixture of a polymeric material and an alignable material isintroduced (e.g., injected) into cavity 67 via port 69. While thecomposite mixture is still liquid, a magnetic field (B) is applied andmaintained along a predetermined direction to align the alignablematerial along the predetermined direction. When the composite mixturecools and solidifies, the alignable material is fixedly oriented alongthe predetermined direction.

Examples of magnetically alignable materials include carbon-containingmaterials (such as carbon single-walled nanotubes, carbon multi-wallednanotubes, and carbon fibers) and ferromagnetic materials. Aferromagnetic material has a magnetic susceptibility of at least about0.075 when measured at 25° C., and can be, for example, a metal (e.g., atransition metal such as nickel, cobalt, or iron), a metal alloy (e.g.,a nickel-iron alloy such as Mu-metal), a metal oxide (e.g., an ironoxide such as magnetite), a ceramic nanomaterial, a soft ferrite (e.g.,nickel-zinc-iron), a magnet alloy (e.g., a rare earth magnet alloy suchas a neodymium-iron-boron alloy or a samarium-cobalt alloy), anamorphous alloy (e.g., iron-silicon-boron), a non-earth alloy, or asilicon alloy (e.g., an iron-zirconium-copper-boron-silicon alloy, aniron-zirconium-copper-boron-silicon alloy). Magnetite is commerciallyavailable from FerroTec Corporation (Nashua, N.H.), under the trade nameEMG 1111 Ferrofluid. Iron-copper-niobium-boron-silicon alloys arecommercially available from Hitachi Metals of America under the tradename Finemet™. Iron-zirconium-copper-boron-silicon alloys arecommercially available from MAGNETEC GmbH under the trade nameNanoperm®.

In certain embodiments, magnetically alignable fibers can have anaverage length of from about 50 nanometers to about 25 microns (e.g.,from about 0.5 micron to about ten microns). Alternatively oradditionally, magnetically alignable fibers can have an average widthand/or diameter of from about 50 nanometers to about 25 microns (e.g.,from about 0.5 micron to about ten microns). In some embodiments, themagnetically alignable material in a polymer composite can be ananomaterial. Nanomaterials include particles and/or fibers having atleast one dimension less than about 1000 nm.

In certain embodiments, magnetically alignable fibers can have anaverage aspect ratio of from about 1:1 to about 10:1 (e.g., from about1:1 to about 5:1).

While magnetically alignable fibers have been shown, other forms ofmagnetically alignable material can be used in a polymer composite. Forexample, the magnetically alignable material can be in the form ofparticles, flakes, and/or a powder.

In some embodiments, the concentration of magnetically alignable fibersin the polymer composite stream can be from about two weight percent toabout 50 weight percent (e.g., from about five weight percent to aboutten weight percent).

Exemplary polymer matrix materials for a polymer composite materialinclude thermoplastics and thermosets. Examples of thermoplasticsinclude, for example, polyolefins; polyamides, such as nylon 12, nylon11, nylon 6/12, nylon 6, and nylon 66; polyesters; polyethers;polyurethanes; polyureas; polyvinyls; polyacrylics; fluoropolymers;copolymers and block copolymers thereof, such as block copolymers ofpolyether and polyamide, e.g., Pebax® (e.g., Pebax® with a relativelyhigh durometer value, such as 50); and mixtures thereof. Examples ofthermosets include elastomers such as EPDM, epichlorohydrin, nitrilebutadiene elastomers, silicones, etc. Conventional thermosets such asepoxies, isocyanates, etc., can also be used. Biocompatible thermosets,for example, biodegradable polycaprolactone, poly(dimethylsiloxane)containing polyurethanes and ureas, and polysiloxanes, may also be used.One or more of these materials can be used in the polymer compositematerial, in any combination.

Other polymer matrix materials include, for example, elastomers such asthermoplastic elastomers and engineering thermoplastic elastomers, suchas polybutylene terephthalate-polyethene glycol block copolymers, whichare available, for example, as HYTREL®. Elastomers are discussed, forexample, in Hamilton U.S. Pat. No. 5,797,877, which is incorporatedherein by reference in its entirety. Other polymers include liquidcrystal polymers (LCP's). Examples of LCPs include polyester(s),polyamide(s) and/or their copolymers, such as VECTRA® A (Ticona),VECTRA® B (Ticona) and VECTRA® LKX (Ticona) (e.g., VECTRA® LKX 1111(Ticona)).

While a tubular member including a single polymer composite has beendescribed, in some embodiments, a medical device can include at leastone polymer composite and at least one polymer (e.g., a polymer that issubstantially free of magnetically alignable material), or at least twodifferent polymer composites.

As an example, FIGS. 7A and 7B show a tubular member 300 that includesone section 310 formed of a polymer 312, and another section 320 formedof a polymer composite 324. Polymer composite 324 includes a polymermatrix 326 and magnetically alignable fibers 328. In region 332 ofsection 320, magnetically alignable fibers 328 have a randomorientation, while in region 334 of section 320, magnetically alignablefibers 328 are aligned parallel to the longitudinal axis “L4” of tubularmember 300. Polymer matrix 326 can be the same polymer as polymer 312,or can be different from polymer 312. Because of the presence ofmagnetically alignable fibers 328 in section 320, and the absence ofmagnetically alignable fibers 328 in section 310, section 320 has ahigher magnetic permeability than section 310. In some embodiments,section 310 can have a magnetic permeability of from about one to about20 (e.g., from about one to about seven). Alternatively or additionally,section 320 can have a magnetic permeability of from about five to about30.

As another example, in some embodiments, a tubular member can includemore than one layer of material. For example, FIGS. 8A and 8B show atubular member 400 that includes an inner layer 410 and an outer layer420. Inner layer 410 includes a polymer 412, while outer layer 420 isformed of a polymer composite 422 that includes a polymer matrix 424 andmagnetically alignable fibers 426. In region 430 of tubular member 400,magnetically alignable fibers 426 are randomly oriented, while in region440 of tubular member 400, magnetically alignable fibers 426 are alignedparallel to the longitudinal axis “L5” of tubular member 400. In someembodiments, polymer matrix 424 of outer layer 420 can include a stiffpolymer, so that the catheter system of which tubular member 400 is apart can be advanced through the body easily (e.g., without kinking orbuckling). Alternatively or additionally, polymer 412 of inner layer 410can be a polymer that gives inner layer 410 a smooth and lubriciousinner surface (e.g., high density polyethylene), to, for example, easepassage of a guide wire through tubular member 400. While inner layer410 is shown including polymer 412 and outer layer 420 is shownincluding polymer composite 422, a multilayer tubular member can includeother arrangements of materials. As an example, a multilayer tubularmember can have an inner layer that includes a polymer composite and anouter layer that includes a polymer. As another example, all of thelayers of a multilayer tubular member can include a polymer composite.As a further example, a multilayer tubular member can have inner andouter layers that include a polymer composite, and an intermediate layerthat includes a polymer.

In some embodiments, the layers of material in a tubular member can havevarying thicknesses. For example, FIG. 9 shows a cross-sectional view ofa tubular member 500 that includes an inner layer 510 and an outer layer520. Layers 510 and 520 have varying thicknesses along the length oftubular member 500. As shown, inner layer 510 includes a polymercomposite 512 that includes a polymer 514 and magnetically alignablematerial 516, and outer layer 520 includes a polymer 522; in otherembodiments, the locations of polymer composite 512 and polymer 522 canbe reversed.

Tubular members (such as those shown in FIGS. 7A, 7B, 8A, 8B, and 9)that include two polymer composites or a polymer and a polymer compositecan be formed, for example, using the tube-forming apparatus 200 shownin FIG. 10. Tube-forming apparatus 200 includes an extrusion head 202, aquench tank 204, a laser micrometer 206, a puller 208, and a cut-offknife 210. Extrusion head 202 has a housing 212 that encloses threesections of the extrusion head: a magnetic field-generating section 220that includes a steel sleeve 222, an iron tip guide 224, and a coil 226(e.g., a solenoid) between iron tip guide 224 and steel sleeve 222, apolymer feed section 230 that includes a first polymer feed 232, and anextrusion die 236. Hollow tip 234 passes through all three sections ofextrusion head 202, and is in fluid communication with first polymerfeed 232.

Polymer feed section 230 of apparatus 200 further includes a secondpolymer feed 242 that, like first polymer feed 232, is in fluidcommunication with tip 234. To form a tubular polymer member, a polymeris added into first polymer feed 232, and a polymer composite is addedinto second polymer feed 242. The polymer and polymer composite aremelted to form liquid polymer and polymer composite streams that entertip 234. The streams are then extruded through extrusion die 236,solidifying upon exposure to the ambient environment and thereby forminga tubular member 250. During the formation of tubular member 250,pressurized air (shown in FIG. 10 as a solid black line) flows throughthe center of hollow tip 234, causing the polymer and polymer compositestreams to form a tubular shape (i.e., tubular member 250). In someembodiments, the polymer and polymer composite streams can be extrudedusing an intermittent extrusion process, such as the process describedin Wang, U.S. Pat. No. 5,533,985, which is incorporated herein byreference in its entirety. In certain embodiments, the polymer andpolymer composite streams can be extruded using a gradient extrusionprocess, such as the process described in Harris, U.S. Pat. No.5,695,789, which is incorporated herein by reference in its entirety.Other methods are described, for example, in U.S. patent applicationSer. No. 10/645,014, filed Aug. 21, 2003, and entitled “MultilayerMedical Devices”; WO 01/32398; and Burlis et al., U.S. Pat. No.3,752,617.

The polymer composite stream that flows through extrusion apparatus 212includes magnetically alignable material. During extrusion and formationof tubular member 250, the polymer composite stream can be exposed to amagnetic field that aligns the magnetically alignable material withinthe polymer composite stream. The magnetic field can be generated byactivating coil 226 (by passing electrical current through the coil).Iron tip guide 224 propagates the magnetic field such that it is presentalong the length of hollow tip 234. Thus, the magnetic field affects thepolymer composite stream as it flows through tip 234 and out throughextrusion die 236.

Because tube-forming apparatus 200 includes two polymer feeds (232 and242), tubular member 250 includes a section that is formed of a polymerand a section that is formed of a polymer composite. Each section can bein the form of a portion of tubular member 250 or a layer of tubularmember 250.

Tubular member 300 of FIGS. 7A and 7B can be formed by deactivating coil226 both during formation of section 310 and during formation of region330 of section 320. The deactivation of coil 226 causes the magneticallyalignable fibers in region 330 to be randomly oriented. However, coil226 is activated when region 332 of section 320 is formed, such that themagnetically alignable fibers in region 320 are aligned parallel to thelongitudinal axis “L2” of tubular member 300.

Tubular member 400 of FIGS. 8A and 8B can be formed by coextrudinglayers 410 and 420, deactivating coil 226 during the formation ofsection 430, and activating coil 226 during the formation of section440. Similarly, tubular member 500 of FIG. 9 can be formed bycoextruding layers 510 and 520, and activating or deactivating coil 226according to the desired level of alignment of magnetically alignablematerial 516 in layer 510.

Materials other than polymers can be incorporated into an extrusionprocess during the formation of a multilayer tubular member. Forexample, an adhesion enhancing material can be incorporated into one ormore material layers. An adhesion enhancing material can be used, forexample, to enhance the adhesion between adjacent layers. Examples ofadhesion enhancing materials include epoxy or anhydride modifiedpolyolefins, such as LOTADER® (Atofina SA), KODAR® PETG (Eastman Kodak),and Plexar® (Equistar Chemicals LP). For example, in embodiments inwhich one layer includes high-density polyethylene and another layerincludes Pebax®, a Plexar® layer can be included between the two layersto enhance adhesion. In some embodiments, an adhesion enhancing materialcan be added to a material (e.g., a composition containing one or morepolymers) prior to extrusion. For example, in embodiments in whichalternate layers are formed of PET and PBT, PETG can be added to the PETbefore extrusion.

In some embodiments, a compatibilizing material can be incorporated intoone or more material layers. In certain embodiments, the compatibilizingmaterial can enhance the compatibility between the layer(s) and one ormore other layers in a multilayer medical device or medical devicecomponent. Examples of such compatibilizing materials includecopolyester elastomers, ethylene unsaturated ester copolymers, such asethylene-maleic anhydride copolymers, copolymers of ethylene and acarboxylic acid or acid derivative, such as ethylene-methyl acrylatecopolymers, polyolefins or ethylene-unsaturated ester copolymers graftedwith functional monomers, such as ethylene-methyl acrylate copolymers,copolymers of ethylene and a carboxylic acid or acid derivative, such asethylene-methyl acrylate maleic anhydride terpolymers, terpolymers ofethylene, unsaturated ester and a carboxylic acid or acid derivative,such as ethylene-methyl acrylate-methacrylic acid terpolymers, maleicacid grafted styrene-ethylene-butadiene-styrene block copolymers, andacrylic acid elastomers, such as acrylic rubbers. Similar polymerscontaining epoxy functional groups, for instance derived from glycidylmethylacrylate (e.g., alkyl(meth)acrylate-ethylene-glycidyl(meth)acrylate polymers) can be used. Ionomeric copolymers can be used.PETG can be used. Examples of compatibilizing materials include HYTREL®HTR-6108, POLYBOND® 3009 (BP Chemicals), SP 2205 (Chevron), DS 1328/60(Chevron), LOTADER® 2400, ESCOR® ATX-320, ESCOR® ATX-325, VAMAC® G1 andLOTADER® AX8660. In certain embodiments, a compatibilizing material(e.g., PETG) can be mixed with one or more polymers (e.g., anLCP-containing material) prior to extrusion.

In some embodiments, a compatibilizing material can be used to enhancethe compatibility between the magnetically alignable material (e.g.,magnetically alignable fibers) and one or more polymers in a medicaldevice or medical device component. Examples of such compatibilizingmaterials include both organic and inorganic materials. Suitable organiccompatibilizing materials can be both low molecular weight molecules andpolymers. Examples of low molecular weight organic compatibilizingmaterials include, but are not limited to, amino acids (e.g.,12-aminododecanoic acid) and thiols. Examples of polymericcompatibilizers include functionalized polymers, such as maleicanhydride containing polyolefins or maleimide-functionalized polyamides.Inorganic compatibilizing materials can include, for example, alkoxidesof silicon, aluminum, titanium, and zirconium. Compatibilizing materialsare further described, for example, in U.S. Published Patent ApplicationNo. 2003/0093107 A1, published on May 15, 2003, which is incorporatedherein by reference.

Other Embodiments

While certain embodiments have been described, the invention is not solimited.

In some embodiments, the tubes and/or methods described herein can beused to form other medical devices or medical device components.Examples of medical devices include catheters (e.g., balloon catheters),balloons, guide wires, endoprosthesis delivery systems (e.g., stentdelivery systems). Balloons are described, for example, in U.S.Published Patent Application No. 2004/0078052 A1, published Apr. 22,2004, which is incorporated herein by reference. Guide wires aredescribed, for example, in Wang et al., U.S. Pat. No. 6,436,056, whichis incorporated herein by reference. Stent delivery systems aredescribed, for example, in Raeder-Devens et al., U.S. Pat. No.6,726,712, which is incorporated herein by reference. In someembodiments, the tubes and/or methods described herein can be used toform a dual lumen catheter with a shaft that includes multiple shaftsections and longitudinally extending lumens that are positioned side byside. Such catheters are described, for example, in Maguire et al., U.S.Pat. No. 4,782,834, which is incorporated herein by reference. In someembodiments, the above-described tubes and/or methods can be used inIntermittent Layer Coextrusion (ILC), which is described, for example,in Wang, U.S. Pat. No. 5,622,665; U.S. Ser. No. 10/645,014, filed onAug. 21, 2004, and entitled “Multilayer Medical Devices”; U.S. Ser. No.10/645,055, filed on Aug. 21, 2003, and entitled “Medical Balloons”; andU.S. Ser. No. 10/787,777, filed on Feb. 26, 2004, and entitled “BalloonCatheter”, all of which are incorporated herein by reference in theirentirety. In certain embodiments, the tubes described herein can have anenhanced ability to conduct low-voltage electricity and can be used, forexample, in endoscopic applications.

For example, and referring now to FIG. 11A, a tube formed by one of theabove-described processes can be used to manufacture a medical balloon600. Medical balloon 600 is formed of a polymer composite 610 thatincludes a polymer 612 and magnetically alignable fibers 614. As shown,fibers 614 are aligned at each of the waist sections 620 and 630 ofballoon 600, and are randomly oriented at the expandable section 640 ofballoon 600. However, in other embodiments, one or both of the waistsections of a balloon can include randomly oriented fibers, and/or theexpandable section of a balloon can include aligned fibers. Also, whileregions 675 of balloon 600 are shown as not including magneticallyalignable material, in some embodiments, regions 675 can includemagnetically alignable material (e.g., magnetically alignable fibers)that is aligned or randomly oriented, or that has an alignment that isbetween the alignment of fibers 614 at waist sections 620 and 630, andthe random orientation of fibers 614 at expandable section 640.

Balloon 600 can be formed, for example, by a blow molding process inwhich a tube is placed (e.g., centered) in a preheated balloon mold, andair is introduced into the tube to maintain the patency of the tubelumen. In some embodiments, after being soaked at a predeterminedtemperature and time, the tube can be stretched for a predetermineddistance at a predetermined time, rate, and temperature. The pressureinside the tube can then be sufficiently increased to radially expandthe tube inside the mold to form the balloon. The formed balloon can beheat treated, for example, to enhance folding memory, and/or folded intoa predetermined profile. The balloon can then be attached to a catheterto form a balloon catheter. Illustrative methods of forming a balloonfrom a tube are described in, for example, commonly-assigned U.S. patentapplication Ser. No. 10/263,225, filed Oct. 2, 2002, and entitled“Medical Balloon”; Anderson, U.S. Pat. No. 6,120,364; Wang, U.S. Pat.No. 5,714,110; and Noddin, U.S. Pat. No. 4,963,313, all of which areincorporated herein by reference in their entirety.

Referring now to FIG. 11B, in some embodiments, the molding of a balloon650 can form relatively thick-walled waist regions 660, which can reducethe flexibility and trackability of the balloon. For example, duringmolding, the body portion 670 of the balloon can be stretcheddiametrically by at least a factor of six. As a result, the balloon wallin body portion 670 can be relatively thin because of the relativelylarge amount of stretching. However, portions of the balloon other thanbody portion 670, such as waist regions 660, may stretch relativelylittle (e.g., by a factor of approximately two). As a result, theportions of balloon 650 other than body portion 670 can remainrelatively thick and can be inflexible. However, the addition ofrandomly oriented magnetically alignable fibers 680 to waist regions 660can enhance the flexibility of the waist regions, while the addition ofaligned magnetically alignable fibers 690 to body portion 670 canenhance the stiffness of body portion 670.

While not shown, in some embodiments, a balloon that includesmagnetically alignable material can also include one or more cuttingelements. Suitable materials for the cutting elements include, forexample, stainless steel and plastic. Balloons with cutting elements aredescribed, for example, in U.S. Published Patent Application No.2003/0163148 A1, published on Aug. 28, 2003; U.S. Published PatentApplication No. 2004/0133223 A1, published on Jul. 8, 2004; and U.S.Ser. No. 10/744,507, filed on Dec. 22, 2003, and entitled “MedicalDevice Systems”, all of which are incorporated herein by reference.

As mentioned above, a tube formed according to one of theabove-described processes can be formed into a guide wire, e.g., apolymer guide wire. Methods of making a guide wire, including one havinggood pushability, are described, for example, in U.S. Pat. No.5,951,494, which is incorporated herein by reference in its entirety.

In certain embodiments, a tubular member can include magneticallyalignable material that is aligned laterally relative to thelongitudinal axis of the tubular member. For example, FIG. 12 shows atubular member 700 formed of a polymer composite 702 that includes apolymer 704 and magnetically alignable fibers 706. Magneticallyalignable fibers 706 are aligned laterally relative to the longitudinalaxis “L6” of tubular member 700.

Tubular member 700 can be formed, for example, using the tube-formingapparatus 800 shown in FIGS. 13A and 13B. Tube-forming apparatus 800includes an extrusion head 810 with a housing 812 enclosing twosections: a polymer feed section 820 including a polymer feed 822, andan extrusion die 830. A hollow tip 840 extends through polymer feedsection 820 and extrusion die 830, and is in fluid communication withpolymer feed 822. Tubular member 700 can be formed similarly to theprocesses described above with reference to apparatus 90 of FIG. 3A andapparatus 200 of FIG. 10. However, tube-forming apparatus 800 generatesa different type of magnetic field from the above-described apparatuses.As shown in FIGS. 13A and 13B, tube-forming apparatus 800 includes amagnet 850, in the bottom 852 of which is embedded a solenoid 860. Whensolenoid 860 is activated (by passing an electrical current through thesolenoid), it generates a magnetic field that is propagated by magnet850 to form a magnetic field force indicated by arrows F1. Thus, as thepolymer composite stream exits extrusion die 830, it is exposed to amagnetic field that causes magnetically alignable fibers 706 to alignlaterally relative to tubular component 700.

In some embodiments, a medical device or medical device component can beformed by extruding a polymer composite through an extrusion head thatincludes a hollow tip and a magnetic mandrel disposed within the hollowtip. The magnetic mandrel can generate a magnetic field that aligns themagnetically alignable material within the polymer composite.

In certain embodiments, a tubular member can be formed by extruding apolymer composite while applying a varying magnetic field to the polymercomposite. For example, a coil (e.g., a solenoid) can be activated (bypassing an electrical current through the coil) to form a magneticfield. The magnetic field can be applied to the polymer composite as thepolymer composite is being extruded. The magnetic field can beselectively reduced, increased, and/or deactivated as the polymercomposite is being extruded, to vary the degree of alignment of themagnetically alignable material in the polymer composite.

In some embodiments, as a tubular member is extruded, the tubular membercan be rotated relative to the longitudinal axis of the tubular member.The rotation of the tubular member as it is being extruded can, forexample, further enhance the rotational or torsional stiffness of thetubular member. Extruded tubing formed by rotation during an extrusionprocess is described, for example, in Zdrahala, U.S. Pat. No. 5,238,305,and in U.S. Ser. No. 10/838,540, filed on May 4, 2004, and entitled“Medical Devices”, both of which are incorporated herein by reference.

In some embodiments, a magnetic field can be applied to a polymercomposite that includes a resin such as a thixotropic resin and, forexample, nanotubes (e.g., carbon nanotubes, ceramic nanotubes). Withoutwishing to be bound by theory, it is believed that the magnetic fieldcan cause the polymers of the thixotropic resin to orient themselvesrelative to the field, and to thereby indirectly orient the nanotubes bypulling the nanotubes along with them. In such embodiments, the magneticfield strength of the magnetic field that is applied to the polymercomposite can be at least about ten Tesla (e.g., at least about 15Tesla, at least about 20 Tesla) and/or at most about 25 Tesla (e.g., atmost about 20 Tesla, at most about 15 Tesla). The orientation of carbonnanotubes in a polymer composite is described, for example, in Choi etal., “Enhancement of Thermal and Electrical Properties of CarbonNanotube Polymer Composites by Magnetic Field Processing,” 94 Journal ofApplied Physics 9 (Nov. 1, 2003), 6034-6039, which is incorporatedherein by reference in its entirety. Extrusion of nanocomposites isdescribed, for example, in U.S. Ser. No. 10/728,079, filed on Dec. 4,2003, and entitled “Medical Devices”, which is incorporated herein byreference.

In certain embodiments, a polymer can be oriented by applying a magneticfield to magnetically alignable material (e.g., magnetically alignablefibers and/or particles) dispersed within the polymer. For example, apolymer composite that includes magnetically alignable fibers can beextruded to form a tubular member. As the middle portion of the tubularmember is being formed, a magnetic field can be applied to the polymercomposite to orient the magnetically alignable fibers in the middleportion with respect to the longitudinal axis of the tubular member. Theorientation of the magnetically alignable fibers can cause thesurrounding polymer to become oriented, as well. As the end portions ofthe tubular member are extruded, the magnetic field can be deactivated,such that the magnetically alignable fibers in the end portions do notbecome oriented with respect to the longitudinal axis of the tubularmember, and thus do not orient the surrounding polymer. After the tubehas been extruded, it can be formed into a balloon (e.g., as describedabove) having a relatively stiff body region (formed out of the middleportion of the tubular member), and relatively flexible waist regions(formed out of the end portions of the tubular member).

In certain embodiments, the above-described balloon can be subjected tostretching, which can have a different effect on different regions ofthe balloon. The stretching can cause the waist regions of the balloonto become relatively thin, but can have little to no effect on thethickness of the body region of the balloon. Thus, the balloon can bestretched in selected regions. As the thickness of the waist regions ofthe balloon decreases, the overall profile of the balloon duringdelivery also decreases, which can enhance the delivery of the balloonto a target site (e.g., by enhancing the pushability and/or trackabilityof the balloon).

In some embodiments, the above-described polymer orientation process canbe used in combination with bump extrusion to produce a tubular memberwith areas of varying thickness and areas of varying orientation. Forexample, a tubular member can be formed with a relatively thick middleportion in which the polymer is oriented, and relatively thin endportions in which the polymer is not oriented. The tubular member canthen be used, for example, to form a balloon having relatively thin andflexible waist regions, and a relatively thick and stiff body region. Incertain embodiments, a balloon that has relatively thin and flexiblewaist regions, and a relatively thick and stiff body region, can haverelatively good compatibility with a sheath of a delivery device such asa catheter. For example, the balloon may be easily wrapped around thedelivery device (e.g., providing a lower profile for delivery) andinserted into and withdrawn from a sheath of the delivery device. Therelatively low profile of the balloon can enhance the deliverability ofthe balloon, and can limit the likelihood of the balloon impeding theability of the delivery device to, for example, cross a vascular lesion.

While a tube-forming apparatus with a coil (e.g., a solenoid) has beenshown, in some embodiments other magnetic-field generating devices canbe used. For example, a tube-forming apparatus can include a hele-shawcell having magnetic parallel plates. Hele-shaw cells are described, forexample, in Walker, “How to Build a Hele-Shaw Cell,” excerpted fromScientific American's The Amateur Scientist (first published October1989).

The methods of making tubular members described herein, such asextrusion and injection molding, can also be applied to makeendoprostheses, such as stent-grafts and covered stents. Referring toFIG. 14, an endoprosthesis 71 includes a stent 73 including a metal oran alloy (such as stainless steel or a shape memory alloy (e.g.,nickel-titanium)), and a tubular member 75 including a composite mixtureof a polymeric material and an alignable material. Tubular member 75 canbe on the exterior surface and/or the interior surface of stent 73. Thecomposite mixture allows tubular member 75 to be made with reducedthickness without compromising the strength of the tubular member, or ifmaintained at the same thickness as a tubular member without thealignable material, further strengthen the tubular member. In someembodiments, tubular member 75 includes a bioerodible polymeric materialand/or a therapeutic agent or drug, e.g., to reduce restenosis orthrombosis. Examples of bioerodible polymers includepolyiminocarbonates, polycarbonates, polyarylates, polylactides, andpolyglycolic esters. Examples of therapeutic agents include non-genetictherapeutic agents, genetic therapeutic agents, vectors for delivery ofgenetic therapeutic agents, cells, and therapeutic agents identified ascandidates for vascular treatment regimens, for example, as agentstargeting restenosis. Therapeutic agents are described, for example, inWeber, U.S. Patent Application Publication No. US 2005/0261760 A1,published on Nov. 24, 2005, and entitled “Medical Devices and Methods ofMaking the Same”, and in Colen et al., U.S. Patent ApplicationPublication No. US 2005/0192657 A1, published on Sep. 1, 2005, andentitled “Medical Devices”.

The endoprosthesis can be made of a desired shape and size (e.g.,coronary stents, aortic stents, peripheral vascular stents,gastrointestinal stents, urology stents, and neurology stents).Depending on the application, the endoprosthesis can have a diameter ofbetween, for example, 1 mm to 46 mm. In certain embodiments, a coronarystent can have an expanded diameter of from about 2 mm to about 6 mm. Insome embodiments, a peripheral stent can have an expanded diameter offrom about 5 mm to about 24 mm. In certain embodiments, agastrointestinal and/or urology stent can have an expanded diameter offrom about 6 mm to about 30 mm. In some embodiments, a neurology stentcan have an expanded diameter of from about 1 mm to about 12 mm. Anabdominal aortic aneurysm (AAA) stent and a thoracic aortic aneurysm(TAA) stent can have a diameter from about 20 mm to about 46 mm.

The endoprostheses described herein can be configured for non-vascularlumens. For example, they can be configured for use in the esophagus orthe prostate. Other lumens include biliary lumens, hepatic lumens,pancreatic lumens, urethral lumens and ureteral lumens.

All publications, applications, and patents referred to in thisapplication are herein incorporated by reference to the same extent asif each individual publication or patent was specifically andindividually indicated to be incorporated by reference in theirentirety.

Other embodiments are within the claims.

What is claimed is:
 1. A method of manufacturing a medical devicecomprising: contacting a non-fluid first tubular member and a secondtubular member, the first tubular member comprising a first polymer andan alignable material different from the first polymer; aligning thealignable material; and bonding the first and second members togetherconcurrent with the step of aligning the alignable material.
 2. Themethod of claim 1, wherein the alignable material is alignedmagnetically.
 3. The method of claim 1, wherein the alignable materialcomprises carbon.
 4. The method of claim 3, wherein the alignablematerial comprises a carbon nanotube or a carbon fiber.
 5. The method ofclaim 1, wherein the first member comprises from about 2 to about 50percent by weight of the alignable material.
 6. The method of claim 1,wherein the first and second members are held in contact by a heatshrink material.
 7. The method of claim 1, wherein the first and secondmembers are bonded by heating at least one of the members.
 8. The methodof claim 1, wherein the first and second members are bonded using alaser.
 9. The method of claim 1, wherein the second member comprises asecond polymer and a second alignable material.
 10. The method of claim1, wherein the fast and second members are components of a ballooncatheter.
 11. The method of claim 1, wherein the first member comprisesfrom about 2 to about 60 percent by weight of the alignable material.12. The method of claim 1, wherein the first member is solidified toform a component of a balloon catheter.
 13. A method of manufacturing atubular medical device or a medical device component having alongitudinal axis, the method comprising: introducing a firstcomposition comprising a first polymer and an alignable material into acavity; aligning the alignable material to have an orientation parallelto the longitudinal axis; and solidifying the first composition in thecavity.
 14. The method of claim 13, wherein the alignable material isaligned magnetically.
 15. The method of claim 13, wherein the alignablematerial comprises carbon.
 16. The method of claim 15, wherein thealignable material comprises a carbon nanotube or a carbon fiber.
 17. Anendoprosthesis, comprising: a metallic tubular structure having a firstend, a second end, a lumen extending from the first end to the secondend and a longitudinal axis extending through the lumen from the firstend to the second end; and a first composition on the tubular structure,the first composition comprising a polymer and an alignable materialcomprising a carbon nanotube or a carbon fiber aligned along a selecteddirection parallel the longitudinal axis.
 18. The endoprosthesis ofclaim 17, wherein the first composition further comprises a drug. 19.The endoprosthesis of claim 17, wherein the first composition comprisesfrom about 2 to about 50 percent by weight of the alignable material.20. The method of claim 1 wherein only a portion of alignable materialis aligned during the aligning step.